Synthesis of diamines



United States Patent 3,205,154 SYNTHESIS OF DIAMINES Irving L. Mador and Louis J. Rekers, Cincinnati, Ohio,

assignors to National Distillers and Chemical Corporation, New York, N.Y., a corporation of Virginia N0 Drawing. Original application Sept. 4, 1958, Ser. No. 758,901, now Patent No. 3,156,729, dated Nov. 10, 1964. Divided and this application Jan. 17, 1961, Ser. No. 83,163

4 Claims. (Cl. 204-74) In Serial No. 609,807 now U.S. Patent No. 2,991,312, as Well as in its continuation-impart Serial No. 758,901, now U.S. Patent No. 3,156,729, of which the present application is a division, processes are disclosed for prepara tion of diamino dimers of conjugated diolefins in which the metal salt that reduces the hydroxylamine is converted in situ to its reductive state.

The present invention relates to an improved process for preparation of diamino derivatives of dimers of diolefins including aliphatic diolefins, cycloaliphatic diolefins, and the like. More specifically, the invention relates to a process for production from butadiene of diamino dimers of butadiene.

In copending application Serial No. 514,399, filed June 9, 1955, now abandoned, a process is disclosed whereby a conjugated diene is subjected to reaction in an aqueous medium in presence of free amino radicals generated in situ under conditions to produce a reaction mixture comprising a diamino product corresponding to addition of one amino radical per unit of the diolefin in a dimer there of. In a specific embodiment, butadiene is reacted in an aqueous medium with free amino radicals generated in situ to produce a reaction product comprising a diamino octadiene which, if desired, can be hydrogenated to the corresponding saturated C diamine. In copending application Serial No. 586,636, filed May 23, 1956, now U.S. Patent No. 3,062,886, a process is disclosed that is an improvement over that of Serial No. 514,399 in that, by use of a controlled amount of a suitable solvent tothe amount of water in the reaction mixture, marked and unexpected improvements in yield of the desired diamino dimer product are obtained. In still another copending application, Serial No. 609,807, filed September 14, 1956, now U.S. Patent No. 2,991,312, a process is disclosed for preparation of such diamino dimers of conjugated diole fins in a substantially non-aqueous reaction system whereby recovery of the desired product is accomplished in a simplified and more economic manner along with obtainment of additional advantages.

Within the scope of such processes wherein the conjugated diolefin is reacted with the free amino radicals formed in situ by oxidation-reduction reaction of a hydroxylamine with a reducing metal ion from a salt of such a metal, and examples of which include titanous chloride, titanous acetate, stannous chloride, manganous chloride, vanadous chloride, etc., a substantially mole to mole ratio of the hydroxylamine to the metal salt is required, as illustrated by the following equation:

In other words, the hereinbefore disclosed processes include extraneous preparation of the metal salt in which the metal is in a lower valent form so as to function as a reducing agent, and addition thereof to the reaction mixture containing the hydroxylamine and conjugated diolefin, or the hydroxylamine is preferably added simultaneously with the reducing metal salt. As illustrated by the foregoing equation, the reducing metal (following reaction with the hydroxylamine) is converted to a higher valent non-reducing form and in the case of titanous chloride (TiCl to TiCl, which upon removal from the re- 3,205,154 Patented Sept. 7, 1965 ICC action mixture, is extraneously reduced to TiCl and recycled to the reaction mixture. As the reducing metal salt represents an expensive component of such a process, desiderata are methods for effecting the selective dimerization reaction with markedly reduced requirement for the amount of metal salt not only from economic considerations but, additionally, as use of markedly reduced amounts of the metal salt facilitate processing for separation of the metal salt from the reaction mixture. Illustrated by the use of titanous chloride as the salt of the reducing metal, difiiculties are presented in separation of the resulting titanium tetrachloride from the desired diamino dimer product in the reaction mixture.

The process embodied herein is directed to a liquid phase process wherein a diolefinic aliphatic hydrocarbon, and particularly a lower molecular weight aliphatic diolefinic hydrocarbon, is reacted with free amino radicals generated in situ by oxidation-reduction reaction of a hydroxylamine and a reducing metal ion from a reducing metal salt and, in which process, the metal salt can be used in markedly reduced amount by carrying out the process under conditions whereby the metal salt, upon conversion in the reaction to its higher valent, non-reductive state, is converted in situ to its reductive state. As embodied herein, the process comprises carrying out the aforedefined reaction under conditions for reducing in situ the higher valent, non-reductive metal salt formed in the reaction by either of a plurality of methods found suitable therefor and inclusive of which are carrying out of the process, simultaneous with formation of the desired diamino product, with catalytic hydrogenation, electrolytic reduction, or use of a suitable metal to reduce the higher valent metal salt, as formed in the reaction, to a reductive state.

For providing free amino radicals, the hydroxylamine is preferably used in the form of a salt and, more preferably, as a salt of hydroxylamine soluble in the reaction medium, inclusive of which are inorganic acid salts such as hydroxylamine hydrochloride, hydroxylamine sulfate, hydroxylamine acetate, etc., as well as monoand di-substituted hydroxylamines of the general formula Where R and R are organic radicals, examples of which are N-benzyl hydroxylamine and N-phenyl hydroxylamine, or where R and R together form a substituted methylene group of the structure R"=NOH, an example of which is acetone oxime. For the reducing metal ion, metal ions including titanous, stannous, manganous, vanadous, chromous, molybdenous and the like, may be used in the form of salts thereof, as, for example, inorganic salts such as chlorides, sulfates, etc., and organic salts, such as acetates, etc. Thus, in practice of this invention, the reaction may be initiated by adding to the reaction mixture a higher valent, non-reducing salt of such metals, (e.g., TiCl whereupon, since the reaction is carried out under conditions whereby such a salt is reduced, the higher valent metal salt is reduced in situ to function as a reducing agent for the hydroxylamine. If desired, the metal salt can be initially added as the lower valent reducing form (e.g., titanous chloride) whereupon, in its conversion to the higher valent form during the reaction, it is reduced in situ to the reducing metal form (e.g., TiCl In carrying out the process of this invention, the reaction between the diolefin and the free amino radicals is carried out in presence of a solvent that is inert with respect to the reactants and the diamine product. For such a purpose, organic solvents including certain oxygen-containing organic solvents are preferred such as, for example, hydroxylic organic solvents, including the alcohols of the methanol series and particularly the relatively low molecular weight members of that series such as methanol, ethanol, isopropanol, and the like; and, generally, such alcohols of from 1 to 4 carbon atoms.

The process embodied herein maybe carried out with use of a diene of which butadiene is particularly well adapted. However, the process may be carried out with use of other conjugated dienes, including for example, such dienes of from four to eight carbon atoms, specific examples of which include isoprene, dimethyl butadiene, the pentadienes, such as methyl 1,3-pentadiene, as well as cyclic dienes such as cyclohexadiene-1,3-pentadiene and cyclopentadiene.

For the described reaction carried out under conditions to eifect the desired in situ reduction of the metal salt, the temperature employed may be varied over a rather wide range such as, for example, from --30 to 100 C. with a preferred range being to 60 C. Though temperature lower than about 0 C. can be used, they are generally not preferred as the reaction rate tends to decrease, Whereas temperatures higher than about 60 C., such as may be used by carrying out the reaction under pressure, are suitable due to an increase in rate of reaction but use of more expensive pressurized vessels is required.

In one embodiment, the reaction is carried out in the presence of a hydrogenation catalyst and hydrogen using, for example, hydrogen pressures of from about atmospheric to 5000 p.s.i. with a preferred range being about 300 to about 1000 p.s.i. and at from about room temperature up to about 100 C., and preferably up to about 60 C.

In another embodiment, the process is carried out under electrolytic conditions for reduction of the higher valent form of the metal salt and, for such a process, a range of current densities of from about 0.01 to about 0.5 ampere/cm. may be used with a preferred range being about 0.05 to about 0.2 and at a temperature maintained at from about to 60 C.

In still another embodiment, the desired reduction of the metal salt is effected by carrying out the process in presence of a metal higher in the electromotive series of elements than the metal of the salt to be reduced in the reaction mixture. Thus, for reducing TiCl suitable meals include zinc, aluminum, tin, iron and others, whereas, for reducing other metal salts such as CrCl reducing metals include zinc and aluminum. Usually, a temperature of from about 10 to 60 C. is suitable for such a reaction with the lesser active metals usually requiring a higher temperature than a more active metal. Thus, for reduction of TiCl a higher temperature is generally employed when a less active metal such as iron is used as compared to a more active metal such as zinc.

In order to further describe the invention, several embodiments thereof are set forth hereinafter. With respect thereto, however, it should be understood that such embodiments are set forth for illustrative and not limitative purposes.

Example 1 Example 2 Anhydrous hydrochloric acid was added to methanol to make a 2 N solution. Hydroxylamine hydrochloride (25 g. or 1.36 moles) was dissolved in this solution, than 1.44 moles butadiene (four times theory) was condensed into the vessel by cooling. Finally, 1.98 ml. titanium tetrachloride (0.018 mole or 5 percent based on hydroxylamine) was added. The solution was placed in an autoclave with mg. Adams catalyst at an initial pressure of 400 p.s.i. During the course of the reaction, the solution was permitted to warm up to room temperature. The final pressure was 280 p.s.i. and the color of the solution was blue indicating that all the hydroxylamine had been consumed.

The solution was reduced in volume by evaporation, following which water and then caustic were added. The resulting diamine layer was taken up in isopropanol and the aqueous layer further extracted with isopropanol. Re moval of the isopropanol by distillation gave 18.4 g. of crude diamine, or a 73% yield of diaminooctane.

Example 3 An autoclave was charged with the following mixture: 250 ml. methanol 2 N in hydrochloric acid, 17.5 g. (0.25 mole) hydroxylamine hydrochloride, 1.38 ml. (0.0125 mole) titanium tetrachloride, and 1.0 mole butadiene. Prereduced Adams catalyst (100 mg.) in methanol was added and the autoclave pressurized to 50 p.s.i. with hydrogen. At the end of the reaction the product was isolated as in the preceding example. The crude product (26.1 g.) was distilled at 0.005 mm. pressure yielding a first cut of C diamine boiling in the range 42 to 85 C.

Example 4 A solution was prepared of 20 g. (0.288 mole) hydroxylamine hydrochloride and 15.8 ml. (0.144 mole) titanium tetrachloride dissolved in 320 ml. methanol, which had previously been made 2 N in anhydrous hydrochloric acid. The electrolytic cell consisted of a 55 x mm. porous alundum crucible in a 400 ml. tall form beaker. The anode was platinum gauze; the cathode, a strip of 1.2 x 34 cm. lead sheet wound as a spiral. A magnetic bar stirrer was used to agitate the contents of the crucible which was the cathode compartment.

The above solution was electrolyzed in two runs, each lasting two hours and twenty minutes. One-half of the solution was added to the cathode cup, and methanol made 2 N in anhydrous hydrochloric acid served as the anolyte. During the course of the electrolysis, butadiene was condensed into the cathode in amount 3.9 times that theoretically required. The cathode temperature was in the range of 24 to 26 C. The current was held at 2.0 amperes and the voltage varied from 4.2 to 5.0 volts. The final solutions were blue due to titanous ion, indicating all the hydroxylamine was destroyed.

The cathode solutions from the two runs were combined and part of the methanol removed by evaporation. Water was added and then caustic to bring the final solution to a 25% concentration in sodium hydroxide, making an allowance for the amount required to new tralize the hydrochloric acid and titanium tetrachloride.

The slurry was extracted With isopropanol to remove the diamine. After evaporation of the solvent, 14.1 g. of crude product was obtained corresponding to a 70% yield based on the hydroxylamine consumed. On distillation at reduced pressure 9.7 g. of octadiene diamine was obtained corresponding to a yield of 48% of theory.

Example 5 A mixture of 200 ml. of methanol 2 N in hydrochloric acid, 10.4 g. (0.15 mole) hydroxylamine hydrochloride, 2.4 ml. titanium tetrachloride, 0.45 mole of butadiene and 9.9 g. of zinc shot cooled to 30 C. was charged to an autoclave. The mixture was allowed to warm to room temperature before shaking was begun. At the conclusion of the reaction, the metal ions were precipitated by addition of caustic and the diamine recoveredby extraction with isopropanol. The yield of crude diaminooctadiene was 6.7 g. or 65 percent of theory basedi on the hydroxylamine charged.

Example 6 A reaction flask was charged with 50 ml. of methanol, 17.4 g. (0.25 mole) hydroxylamine hydrochloride, 2.7 ml. (0.025 mole) of titanium tetrachloride and 9.8 g. of zinc dust. Over a five minute period 180 ml. of methanol 2 N in hydrochloric acid was added to the flask, and 0.50 mole butadiene condensed in by means of a Dry Ice reflux condenser. Rapid stirring and external cooling were supplied and the reaction temperature was in the range 20 to 24 C. At the end of the five minute period, solution of the zinc was essentially complete. Eleven percent of the hydroxylamine was found to be remaining. The crude yield of 10.5 g. represented 68 percent of theory, based on the hydroxylamine consumed, of C diamine.

Example 7 A reaction was carried out similar to Example 6 using 8.4 g. of 100 mesh iron powder instead of zinc. The amount of butadiene was increased to 0.75 mole. The addition time was minutes and the temperature 10 C. from which there was obtained a 44 percent of theory yield of diaminooctadiene.

Example 8 A reaction was carried out similar to Example 7 but on a 40 percent larger scale and using 24.9 g. of 50 mesh tin in place of iron. The yield of diamine octadiene was 10 percent of theory based on the hydroxylamine charged.

Irrespective of the method used for effecting the desired in situ reduction of the metal salt, the process embodied herein enables utilization of substantially less than an equivalent amount of the metal salt for reduction of the hydroxylamine. Generally, the amount of metal salt employed may range from one to 20 mole percent based on the amount of hydroxylamine or hydroxylamine salt that is employed and, preferably, a range of from about 2 to about 10 mole percent. With respect to the proportional amounts of the diolefin and hydroxylamine, substantially equivalent amounts thereof may be used but, preferably, an excess of the diolefin such as up to about 8 equivalents is satisfactory and, preferably, from about 2 to about 4 equivalents, with the excess diolefin being recovered at the end of the reaction.

The process embodied herein can be carried out, if desired, in an aqueous medium containing a solvent as aforedefined with water being added initially if desired, or as an aqueous solution of the hydroxylamine reactant. Preferably, when a water-soluble hydroxylamine salt is used, addition of water is preferred to increase the solubility of the hydroxylamine salt in the reaction mixture. Such addition of water is particularly preferred in cases where the reaction medium contains a higher alcohol as a solvent for the diolefin.

For obtaining optimum yields of the desired diamino dimer product, addition of an acid is preferred and in some cases required. For such a purpose, examples of acids include hydrochloric, sulfuric, and acetic, and generally, in a concentration to provide a normality of from about 1 N to about 6 N with a preferred range being 2 N to 4 N. For such a purpose, anhydrous or aqueous acid solutions may be used.

The diamino products produced by practice of this invention possess utility for many purposes and, particularly, are suitable upon hydrogenation to provide saturated, relatively high molecular weight amines that are useful for reaction with dibasic acids, such as sebacic acid, adipic acid and the like, to form synthetic linear polyamides that are fiber-forming into fibers of excellent cold-drawn characteristics. For example, the C unsaturated diamines produced by certain embodiments described and subjected to hydrogenation to the corresponding saturated C diamines, as well as the C saturated diamines produced directly in the catalytic hydrogenation embodiment, provide upon being subjected to condensation polymerization reactions with an acid such as sebacic acid, adipic acid, and the like, synthetic linear condensation polyamides that are fiber-forming to fibers of excellent cold-drawn characteristics.

Although it is not intended that the invention be bound by any theory as to the particular reactions that occur in the processing of conjugated dienes to produce the diamino derivatives thereof as embodied herein, it is believed that the following reactions occur when, for illustrative purposes, the reactants include butadiene and the free radical is an NH radical such as formed by oxidation-reduction reaction of hydroxylamine hydrochloride and t-itanous chloride.

While there are above disclosed but a limited number of embodiments of the process of the invention herein presented, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed, and it is desired therefore that only such limitations be imposed on the appended claims as are stated therein.

We claim:

1. In a process for preparing diamino dimers of a lower molecular weight aliphatic conjugated diolefinic hydrocarbon by maintaining in liquid phase a reaction mixture comprising a lower molecular weight aliphatic conjugated diolefinic hydrocarbon and, in said mixture, reacting a hydroxylamine with a salt of a multivalent metal that reduces said hydroxylamine whereby the metal salt is oxidized to a higher valent non-reducing form, the improvement which comprises carrying out said reaction in an electrolytic cell at a current density of from about 0.01 to about 0.5 ampere/cm. to reduce in situ to reducing form the metal that is oxidized in reduction of the hydroxylamine, the reaction mixture containing from one to twenty mole percent of the metal salt based on the amount of hydroxylamine and, in ratio of equivalents, from about one to about eight of the diolefin to one of the hydroxylamine.

2. A process, as defined in claim 1, wherein the diolefin is butadiene, and the metal salt is titanous chloride.

3. A process, as defined in claim 1, wherein an acid is added to the reaction mixture to provide a normality of from 1 N to 6 N.

4. A process, as defined in claim 1, wherein the reaction is carried out at from about 10 to about 60 C.

References Cited by the Examiner UNITED STATES PATENTS 723,217 3/03 Spence 204-94 2,567,109 '9/51 Howard 260-784 2,798,039 7/57 Inoue et al. 204-94 2,983,758 5/61 Hoover 260-583 3,017,435 1/62 Colfrnan et al. 260-583 OTHER REFERENCES Davis et al.: Journal Chem. Soc., pages 2563-7 (1951), Part III.

Schumb et al.: Journal Am. Chem. Soc., volume 55, pages 596-7 (1933).

WINSTON A. DOUGLAS, Primary Examiner.

JOHN R. SPECK, MURRAY TILLMAN, Examiners. 

1. IN A PROCESS FOR PREPARING DIAMINO DIMERS OF A LOWER MOLECULAR WEIGHT ALIPHATIC CONJUGATED DIOLEFINIC HYDROCARBON BY MAINTAINING IN LIQUID PHASE A REACTION MIXTURE COMPRISING A LOWER MOLECULAR WEIGHT ALIPHATIC CONJUGATED DIOLEFINIC HYDROCARBON AND, IN SAID MIXTURE, REACTING A HYDROXYLAMINE WITH A SALT OF A MULTIVALENT METAL THAT REDUCES SAID HYDROXYLAMINE WHREBY THE METAL SALT IS OXIDIZED TO A HIGHER VALENT NON-REDUCING FORM, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID REACTION IN AN ELECTROLYTIC CELL AT A CURRENT DESITY OF FROM ABOUT 0.01 TO ABOUT 0.5 AMPERE/CM.2 TO REDUCE IN SITU TO REDUCING FORM THE METAL THAT IS OXIDIZED IN REDUCTION OF THE HYDROXYLAMINE, THE REACTION MIXTURE CONTAINING FROM ONE TO TWENTY MOLE PERCENT OF THE METAL SALT BASED ON THE AMOUNT OF HYDROXYLAMINE AND, IN RATIO OF EQUIVALENTS, FROM ABOUT ONE TO ABOUT EIGHT OF THE DIOLEFIN TO ONE OF THE HYDROXYLAMINE. 